Electric furnace.



G. HO-LMGREN. ELECTRIC FURNACE.

A PPLIUATION FILED MAB. 6, 1907.

'PATEN'I'ED use. 17. 190?.

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PATENTED DEC. 17-, 1907.

'-G. H OLMG'RENJ; ELECTRIC FURNACE. APPLICATION FILED MAR. e, 1007.

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vPATENTED DEC. 17, 190?. G. HOLMGREN. ELECTRIC FURNAGE. APPLIOATION FILED MAB. e, 1907.

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Specification of Letters Patent.

Patented Dec. 17, 1907.

Application filed amt c.1907. swarm. 360.988.

T 0 as within it may con-ct n i i i a" 1 it iniownthat .I, GUsrAr DLOLMGREN, a

-' citizenof theKingclom of Sweden, residing at W esteras, Sweden, have invented new and useful improvements in Electric Furnaces, of which-the foilowing is a specification; This invention relates to improvements electric furnaces; j

A; weil known it has been nroposed to use ior metallurgical ric generators with rotatingfield magnet v and'stationary armature on which latter the instailurgical hath forms a short-circuited,

induced conductor. In such furnacvs heretoiore' known the field-magnet rotates aro und Qa horizontal she-ft but as also the hath in the most cases should have a horizontal position one has been limited to the'use of field-1nagnets and armatures having only two poles.

Such a construction suilers, however, iroin several important disadvantages among which may bernentioned the violent vibrations arising during, the operation of the furnace on account of the magnetic circuit being more or less fullybrolzen two times during each revolution of the rotating fieldmagnet.

that the torque varies not only between null and a maximum but between positive and negative values which increases the vibrations in the furnace.

The object of the present invention is to provide an electric generator furnace, in which the said inconveniences are removed The invention consists, principally, in that the field-magnet oi the furnace is rotatable around a vertical shaft. such arrangementlt will be possible to build furnaces with any number of poles and any numurposes eie'ctric furnaces carried out according to the principle otelec- Further the inevitable'great self hath.

induction in such single-phase furnace effects orator on line Elk-Hi in Fig. 4, and Fig. 4 is a horizontal section thereof. Fig. 5 is a diagrammatic view of theiurnace shown in Figs; 3 and 4. Fig. 6 isa horizontal section of a poly phase inrnace embodying my invention and Fig. 7 iliustrates diagrammaticaliy the poie-arrangement in said furnace.

Figs. 8' and 9 are views corresponding to. Figs. 6 and 7 oi a second polyphase furnace.-

The furnace shown in Figs i and 2 has a U-shaped upright armaturecore 1 around the vertical shanks of which the. meltingbath :2 of the furnace forms two closed circuits communicating with each other. The rotatable fieldcnagnet 3 has a vertical shaft 4 and two poles of segmental shape correspondingto. the of the pole-surfaces of the arinaturecore. magnet 3 is in the position shown in Fig. 1 in relation to the armature-core, the magnetic circuit is closed through both circuits of the nielting-hath When the field-magnet has been turned 90 from the said position each half of the magnet circuit of the same is closed through one of the armature poles so that the magnetic flux does not pass through the closed circuits formed by the melting Nevertheless it is possible by giving the pole-pieces suitable dimensions to keep the total magnetic flux through the air-gap between the field andarmaturecores 'suhstantially constant. The variation of the number of lines of force inducing the meltingbath and of those short-circuited by the pole.- pieces of the iron-cores takes place successively whereby vibrations in the ironcores will in a very high degree be avoided and the sei'f induction of the furnace will be comparatively low.

Figs. 35' show multi-pole furnace, the melting-bath '2 being arranged as a six-pole, single-phase short-circui-ted windin having one conducor lor each slot and po e, while the field-magnet in accordance therewith has siX poles. The arrnaturewore l is annular andis provided with slots through which the -brickwork inclosing thev melting-bath passes.

in tllGiOIIll shown in Figs. 6 and 7 the melting-oath is so divided that the same corresponds. to the winding of athree-pole generator or the short-circuited winding of an induction motor having a six ole fieldmagnet. In Figs. 5 and 7 the po es of the When the field field-magnet are indicated 'by N and S, While 5 indicates the teeth of the armature-core and 6 cross-sections of the bath.

The furnace shown in Figs. 8 and 9 has a four-pole field-magnet and 'a melting-chamberconsisting of two concentric channels 7 and 8 connected to each other by means of radial channels 9 placed at a distance from each other corresponding to 2/3 of the pole' pitch.. The said-furnace corresponds to a' three phase generatonhaving so called short coilsv and has the advantage of a small selfinduction on account of the reduction of the currents flowin through the radial parts of the meltin batih The fiel magnet in the formsshown in 'Figs. 69 may be carried out substantially in the same manner as in Fig. 3.

It is'obvious that the invention is not limited to the forms shown in the drawings, in as much as the same may be modified as to the number of phases and poles at will. The field-magnet is shown as. arranged below the armature-core but obviously it may be arranged above the same if desired.

The furnaces in question, especially those having closed concentric circuits, may advantageously be built as shaft-furnaces haying the shaft arranged above parts of the bath, for instance the inner circuit or above the Whole bath.

By dividing the melting-bath in two or more circuits a reduction of the self-induction of the furnace caused by the reduction of the current in each circuit will be obtained, While by the multi-phase arrangement a substantially constant torque of the furnace Will beefi'ected.

Havin now described my invention,

what I c aim and desire to secure by Letters 40 Patent is: t g

1. In, an electric induction furnace the combination of -a stationary iron core, a melting chamber in'closing said iron core, a rotary magnet, and'a vertical shaft for said magnet. I

2. In an electric induction furnace the combination of a stationary iron core, poles being provided on said iron core for form ng a number of magnetic circuits, a meltm chamber, a rotary magnet,-. and a vertica shaft'for said magnet 3. In an electricgmduction furnace the combination of a stationaryiron core, poles being provided on said iron core for forming 5t a number of magnetic circuits, two concentric melting chambers, radial channels between the poles of thesaid iron core con-' meeting the said chambers, a multi-pole rotary magnet, and avertical shaft for said magnet. I

4. In an electricinduction furnace the conibination ofa stationary'iron core, poles 

